Two Major Groups

Classifying fungi into ascomycetes and basidiomycetes

The (macro) fungi that are dealt with in this website can be divided into
two broad groups, called ascomycetes and basidiomycetes, depending
on how their sexual spores are formed. All the macrofungi produce sexual spores,
which result from the combination of genetic information from two parents. The
function of the fruiting bodies described in the TYPES
OF FUNGI SECTION is to produce and disperse sexual spores. However, many
macrofungal species may also produce asexual spores - but not in such easily
visible structures as those that produce the sexual spores. For the sake of
brevity, the simple word "spore" will be used throughout this section but it
will always mean "sexual spore", since only the sexual spores are relevant here.

Ascomycetes

In ascomycetes the spores are produced within microscopic cells called asci.
The asci vary in shape from cylindric to spherical. Commonly, each ascus holds
eight spores - but there are species with just one spore per ascus and others
with over a hundred spores per ascus.

Here are some drawings of asci. If you click on the camera you will see a photo
of the corresponding fruiting body. To give you an idea of size, the short black
line in each drawing represents a hundredth of a millimetre. Notice the one
large spore per ascus in the Tuber.

Leotia lubrica

Trichoglossum walteri

Tuber sp.

Of the fruiting bodies described in the TYPES
OF FUNGI section, the cup (or disk) fungi and the flask fungi are ascomycetes;
the truffle-like fungi include both ascomycetes and basidiomycetes. The links
below will show you where the asci are found in the different types of fruiting
bodies. The diagrams that will help in the explanations are stylized, often
with the size of the asci exaggerated (to show them more easily). Despite
this, the diagrams will illustrate the nature of many of the ascomycete fruiting
bodies you are likely to see.

Basidiomycetes

In basidiomycetes the spores develop on projections that grow out from microscopic
cells called basidia, rather than being enveloped within cells. In most
cases the basidia are elongated and club-like, though there is variation in
shape. Commonly, each basidium has four projections and four spores -
but some species may have just one projection and spore per basidium and others
up to eight. In most basidiomycetes the basidia have no dividing walls (or septa),
but in a small number of genera the basidia are septate. The projections from
the basidia are called sterigmata (singular: sterigma).

Here are some drawings of basidia from various fungi. Some basidia are shown
with spores, some have already released their spores. If you click on the camera
icon, you will see a photo of the corresponding fruiting body. To give you an
idea of size, the short black line in each drawing represents a hundredth of
a millimetre. It is not hard to see why the basidia in Dacryopinax are
called "tuning-fork"basidia.

Basidia with no septa:

Amanita phalloides
(the Deathcap mushroom)

Botryobasidium sp.

Dacryopinax spathularia

Basidia with septa:

Auricularia sp

Tremella fuciformis

Most of the types of fruiting bodies described in the TYPES
OF FUNGI section are produced by basidiomycetes. Remember that there are
both ascomycete and basidiomycete truffle-like fungi. The links below will show
you where the basidia are found in the different types of fruiting bodies. The
diagrams that will help in the explanations are stylized, often with the size
of the basidia exaggerated (to show them more easily). Despite this, the diagrams
will illustrate the nature of many of the basidiomycete fruiting bodies you
are likely to see.